Waterborne acrylic dispersions are well known as binders in the production of coating compositions such as plasters, renders, and paints. Advantages of using waterborne systems for such applications include low cost, ease of application and cleanup, reduced drying times, and low or no odor or emissions of volatile organic compounds (VOC). Currently, most acrylic dispersions are produced using monomers derived from oil based sources, i.e., fossil fuels. However, the movement toward environmental sustainability has provided an impetus for the development of copolymers utilizing as much raw material fitting within a sustainable framework as possible. For example, the LEED Green Building Rating System® requires that materials incorporate 5% of rapidly renewable materials. Providing binders or coatings that can be utilized in building materials to help meet the requirements of the LEED Green Building Rating System® would be beneficial to the environment. However, it is also important that the binders or coatings maintain or even improve the properties that make them beneficial for their particular use.
For example, US Patent Application Publication No. 2014/0065435 discloses an aqueous polymer dispersion comprising a vinyl polymer with at least two phases comprising: A) 40 to 90 wt. % of a vinyl polymer A having a glass transition temperature in the range of from −50 to 30° C.; and B) 10 to 60 wt. % of a vinyl polymer B having a glass transition temperature the range of from 50 to 130° C.; wherein vinyl polymer A comprises 0.1 to 10 wt. % of at least one acid-functional olefinically unsaturated monomer, wherein at least 20 wt. % of the monomer composition used to form vinyl polymer A and vinyl polymer B is derived from at least one bio-renewable olefinically unsaturated monomer. Examples of suitable bio-renewable monomers are said to include (meth)acrylic acid and alkyl (meth)acrylate, where alkyl is preferably selected from methyl, ethyl, butyl or 2-ethylhexyl. The aqueous polymer dispersion is reported to be useful in coating compositions having an advantageous combination of a low minimum film forming temperature (MFFT) and good anti-blocking properties.
Similarly, US Patent Application Publication No. 2014/0058031 discloses an aqueous polymer coating composition comprising at least: a vinyl polymer A having a weight average molecular weight Mw within the range of from 1,000 to 150,000 g/mol and an acid value >5 mg KOH/g; and a vinyl polymer B having a weight average molecular weight of at least 80,000 g/mol and an acid value <35 mg KOH/g; wherein I) the wt. % of olefinically unsaturated monomers used to form polymer A and polymer B are in the ratio of 5:70 to 95:30 and add up to 100%; II) at least 20 wt. % of at least one of polymer A and or polymer B is derived from at least one bio-renewable olefinically unsaturated monomer. In addition to (meth)acrylic acid and alkyl (meth)acrylates, suitable bio-renewable monomers are said to include α-methylene butyrolactone, α-methylene valerolactone, α-methylene γ-R1 butyrolactone (wherein R1 can be alkyl or aryl); itaconates such as dialkyl itaconates and monoalkyl itaconates, itaconic acid, itaconic anhydride, crotonic acid and alkyl esters thereof, citraconic acid and alkyl esters thereof, methylene malonic acid and its mono and dialkyl esters, citraconic anhydride, mesaconic acid and alkyl esters thereof. Improved properties are said to include heat resistance, colloidal stability, pigment compatibility, surface activity, blocking resistance and reduced MFFT depending on the monomers used.
U.S. Pat. No. 8,889,783 discloses a binder or coating composition comprising: (A) a copolymer derived from monomers comprising: a vinyl aromatic monomer; a second monomer selected from the group consisting of butadiene, alkyl acrylates, alkyl methacrylates, and mixtures thereof; and a biobased monomer, wherein the copolymer has a biobased carbon content of 10 to 95 weight percent, based on the weight of the copolymer, and the median particle size of the copolymer is 80 nm to 200 nm; and (B) a coating pigment, mineral filler, or mixture thereof, wherein the coating pigment, mineral filler, or mixture thereof is present in an amount of 60 to 90 weight percent, based on the weight of the binder or coating composition. Examples of biobased monomers include isobornyl acrylate, isobornyl methacrylate, tetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate, lauryl acrylate, lauryl methacrylate, and mixtures thereof. The coating compositions are described as being useful as paper coatings, carpet backing, paints, surface coatings, and binders.
International Patent Publication No. WO 2016/128574 A1 discloses an aqueous polymer emulsion comprising at least 30 wt. % of a vinyl copolymer (A), said vinyl copolymer comprising: (I) from 10 to 90 wt. % of 2-octyl acrylate monomer; (II) from 10 to 90 wt. % of at least one itaconate ester monomer according to formula (1):
in which A and B may be different or the same and A and B are independently methyl or ethyl; and (III) from 0 to 80 wt. % of ethylenically unsaturated monomer other than (I) and (II); whereby the summed amount of (I), (II) and (III) is 100 wt. % and whereby the amount of vinyl copolymer (A) is given relative to the total weight amount of the polymers present in the emulsion. The itaconate ester monomer according to formula (1) can be produced from biobased itaconic acid and the polymer emulsion is reported to give coatings with a high water resistance.
According to the present invention, it has now been found that an acrylic polymer dispersion produced from a specific combination of a hard meth (acrylic acid) ester with high biorenewable content, a soft meth (acrylic acid) ester and an acidic comonomer can be used as binder for paints and coatings to provide excellent wet scrub resistance and outdoor performance.